netdev - Re: [PATCH net-next v3 02/11] net: phy: introduce phy_has_c45

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Date: Tue, 05 Sep 2023 10:22:40 +0200
From: Michael Walle <mwalle@...nel.org>
To: "Russell King (Oracle)" <linux@...linux.org.uk>
Cc: Andrew Lunn <andrew@...n.ch>, Heiner Kallweit <hkallweit1@...il.com>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Yisen
 Zhuang <yisen.zhuang@...wei.com>, Salil Mehta <salil.mehta@...wei.com>,
 Florian Fainelli <florian.fainelli@...adcom.com>, Broadcom internal kernel
 review list <bcm-kernel-feedback-list@...adcom.com>, Marek Behún <kabel@...nel.org>, Xu Liang <lxu@...linear.com>,
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org, Simon Horman
 <simon.horman@...igine.com>
Subject: Re: [PATCH net-next v3 02/11] net: phy: introduce
 phy_has_c45_registers()

Hi,

> Hence why I disagree with your suggestion.

So how can we make progress here? I tried Russells suggestion using
phy_supports_c45_transfers() and phy_has_c22_registers(). You can find
a possible v4 of this series on my github [1].

Some uses of .is_c45 seem to be to test whether the c45_ids are valid. 
E.g.
from the phy.h:
* @c45_ids: 802.3-c45 Device Identifiers if is_c45.

But if you test if a bit is set, you can skip that. For the opposite 
test
you'd need to have some kind of indication whether c45_ids was populated
in the first place.

If you convert all these uses of is_c45, there will only be a handful
of uses left. And replacing these by phy_supports_c45_transfers() sounds
sane to me except for for these two:
(1) drivers/net/ethernet/hisilicon/hns/hns_ethtool.c
(2) drivers/net/phy/mxl-gpy.c

(2) will eventually replaced by my phy_promote_to_c45(). I might reorder
the patches, so I'll get rid of the .is_c45 use there before the
conversion to phy_supports_c45_transfers().

But honestly, for (1) I don't have any idea whats going on. If I look
at the very first commit, it seems that the is_c45 property is used
to distinguish loopback handling between a gigabit and a 10g PHY (?).

Btw, Russell, I've noticed that phy_restart_aneg() and phy_config_aneg()
will test for c22 registers, but phy_aneg_done() tests just for .is_c45.
Is that correct?

-michael

[1] https://github.com/mwalle/linux/tree/feature-c45-over-c22-v4
[2] 
https://git.kernel.org/torvalds/c/b5996f11ea5496d0445078f47d22c987888ed467